Lateral root elongation in maize is related to auxin synthesis and transportation mediated by N metabolism under a mixed NO_(3)^(–) and NH_(4)^(+) supply

A mixed nitrate (NO_(3)^(–)) and ammonium (NH_(4)^(+)) supply can promote root growth in maize (Zea mays),however,the changes in root morphology and the related physiological mechanism under different N forms are still unclear.Here,maize seedlings were grown hydroponically with three N supplied in three different forms (NO_(3)^(–)only,75/25 NO_(3)^(–)/NH_(4)^(+)and NH_(4)^(+)only).Compared with sole NO_(3)^(–)or NH_(4)^(+),the mixed N supply increased the total root length of maize but did not affect the number of axial roots.The main reason was the increased total lateral root length,while the average lateral root (LR) length in each axle was only slightly increased.In addition,the average LR density of 2nd whorl crown root under mixed N was also increased.Compared with sole nitrate,mixed N could improve the N metabolism of roots (such as the N influx rate,nitrate reductase (NR) and glutamine synthase (GS)enzyme activities and total amino content of the roots).Experiments with exogenously added NR and GS inhibitors suggested that the increase in the average LR length under mixed N was related to the process of N assimilation,and whether the NR mediated NO synthesis participates in this process needs further exploration.Meanwhile,an investigation of the changes in root-shoot ratio and carbon (C) concentration showed that C transportation from shoots to roots may not be the key factor in mediating lateral root elongation,and the changes in the sugar concentration in roots further proved this conclusion.Furthermore,the synthesis and transportation of auxin in axial roots may play a key role in lateral root elongation,in which the expression of ZmPIN1B and ZmPIN9 may be involved in this pathway.This study preliminarily clarified the changes in root morphology and explored the possible physiological mechanism under a mixed N supply in maize,which may provide some theoretical basis for the cultivation of crop varieties with high N efficiency.

Does the root to shoot ratio show a hormetic response to stress? An ecological and environmental perspective

Root/shoot(R/S)ratio is an important index for assessing plant health,and has received increased attention in the last decades as a sensitive indicator of plant stress induced by chemical or physical agents.The R/S ratio has been discussed in the context of ecological theory and its potential importance in ecological succession,where species follow different strategies for above-ground growth for light or below-ground competition for water and nutrients.We present evidence showing the R/S ratio follows a biphasic dose–response relationship under stress,typical of hormesis.The R/S ratio in response to stress has been widely compared among species and ecological succession classes.It is constrained by a variety of factors such as ontogeny.Furthermore,the current literature lacks dose-response studies incorporating the full dose–response continuum,hence limiting scientific understanding and possible valuable application.The data presented provide an important perspective for new-generation studies that can advance current ecological understanding and improve carbon storage estimates by R/S ratio considerations.Hormetic response of the R/S ratio can have an important role in forestry for producing seedlings with desired characteristics to achieve maximum health/productivity and resilience under plantation conditions.

Distribution and tensile strength of Hornbeam （Carpinus betulus） roots growing on slopes of Caspian Forests, Iran

Biomechanical characteristics of the root system of hornbeam （Carpinus betulus） were assessed by measuring Root Area Ratio （RAR） values and tensile strength of root specimens of eight hornbeam trees growing on hilly terrain of Northern Iran. RAR values of the roots were obtained using profile trenching method at soil depth of the top 0.1 m. In total 123 root specimens were analyzed for tensile strength. Results indicate that in general, RAR decreases with depth, following a power function. The RAR values in up and down slopes have no significant statistical differences. In most cases, the maximum RAR values were located in soil depth of the top 0.1 m, with maximum rooting depth at about 0.75 m. The minimum and maximum RAR values along the profiles were 0.004% and 6.431% for down slope and 0.004% and 3.995% for up slope, respectively. The number of roots in the up and down slope trenches was not significantly different. In the same manner as for RAR, number of roots distributing with depth was satisfactorily approximated a power function. The penetration depths of above 90 percent of the roots were at soil depths of 50 cm and 60 cm for up and down slopes, respectively. Results of Spearman＇s bivariate correlation showed no significant correlation between the RAR value with tree diameter and gradient of slope and number of roots. The mean value of root tensile strength was 31.51 ± 1.05 MPa and root tensile strength decreased with the increase in root diameter, following a power law equation. Using ANCOVA, we found intraspecies variation of tensile strength.

Soil fixation and erosion control by Haloxylon persicum roots in arid lands, Iran

Vegetation roots contribute to soil fixation and reinforcement, thus improving soil resistance against erosion. Generally, the amount of soil fixation presented by roots mainly depends on root density and tensile strength. In the present study, we conducted the research in order to further understand the biotechnical properties of Haloxylon persicum and also to quantify its role in increasing soil cohesion in arid lands of Iran. Ten H. persicum shrubs were randomly selected for root distribution and strength investigations, in which five samples were set on flat terrain and other five samples on a moderate slope terrain. The profile trench method was used to assess the root area ratio(RAR) as the index of root density and distribution. Two profiles were dug around each sample, up and downslope for sloped treatment and north and south sides for flat treatment. The results showed that RAR increased with increasing soil depth and significantly decreased in 40–50 cm layers of downhill(0.320%) and 50–60 cm for uphill(0.210%). The minimum values for the northward and southward profiles were 0.003% and 0.003%, respectively, while the maximum values were 0.260% and 0.040%, respectively. The relationship between the diameter of root samples and root tensile strength followed a negative power function, but tensile force increased with increasing root diameter following a positive power function. The pattern of increased cohesion changes in soil profile was relatively similar to RAR curves. The maximum increased cohesion due to the presence of roots in uphill and downhill sides were 0.470 and 1.400 kPa, respectively. In the flat treatment, the maximum increased cohesions were 0.570 and 0.610 kPa in northward and southward profiles, respectively. The analysis of variance showed that wind and slope induced stresses did not have any significant effect on the amount of increased cohesion of H. persicum. The findings served to develop knowledge about biotechnical properties of H. persicum root system that can assist in assessing the efficiency of afforestation and restoration measures for erosion control in arid lands.

Distribution and tensile strength of Hornbeam(Carpinus betulus) roots growing on slopes of Caspian Forests,Iran

Biomechanical characteristics of the root system of hornbeam(Carpinus betulus) were assessed by measuring Root Area Ratio(RAR) values and tensile strength of root specimens of eight hornbeam trees growing on hilly terrain of Northern Iran.RAR values of the roots were obtained using profile trenching method at soil depth of the top 0.1 m.In total 123 root specimens were analyzed for tensile strength.Results indicate that in general, RAR decreases with depth, following a power function.The RAR values in up and down slopes have no significant statistical differences.In most cases, the maximum RAR values were located in soil depth of the top 0.1 m, with maximum rooting depth at about 0.75 m.The minimum and maximum RAR values along the profiles were 0.004% and 6.431% for down slope and 0.004% and 3.995% for up slope, respectively.The number of roots in the up and down slope trenches was not significantly different.In the same manner as for RAR, number of roots distributing with depth was satisfactorily approximated a power function.The penetration depths of above 90 percent of the roots were at soil depths of 50 cm and 60 cm for up and down slopes, respectively.Results of Spearman's bivariate correlation showed no significant correlation between the RAR value with tree diameter and gradient of slope and number of roots.The mean value of root tensile strength was 31.51 ± 1.05 MPa and root tensile strength decreased with the increase in root diameter, follow-ing a power law equation.Using ANCOVA, we found intraspecies variation of tensile strength.

Water Deficit Stress Effects on Corn (<i>Zea mays</i>, L.) Root:Shoot Ratio

A study was conducted at Akron, CO, USA, on a Weld silt loam in 2004 to quantify the effects of water deficit stress on corn (Zea mays, L.) root and shoot biomass. Corn plants were grown under a range of soil bulk density and water conditions caused by previous tillage, crop rotation, and irrigation management. Water deficit stress (Dstress) was quantified by the number of days when the water content in the surface 0.3 m deviated from the water content range determined by the Least Limiting Water Range (LLWR). Root and shoot samples were collected at the V6, V12, and R1 growth stages. There was no significant correlation between Dstress and shoot or root biomass at the V6 growth stage. At the V12 and R1 growth stages, there were negative, linear correlations among Dstress and both root biomass and shoot biomass. The proportional decrease of shoot biomass was greater than the proportional decrease in root biomass, leading to an increase in the root:shoot ratio as water deficit stress increased at all growth stages. Determining restrictive soil conditions using the LLWR may be useful for evaluating improvement or degradation of the soil physical environment caused by soil management.

Effects of Free-air CO2 Enrichment on Root Characteristics and C:N Ratio of Rice at the Heading Stage

A hydroponics experiment was conducted to investigate the rice root growth in FACE （free-air carbon dioxide enrichment）. The root biomass, root volume, ratio of root/shoot, number of adventitious roots and root diameter significantly increased under FACE conditions, while the CO2 enrichment decreased the N concentration in rice roots without any change in the C content, leading to an increase in root C：N ratio. Moreover, the elevated CO2 resulted in a remarkable decrease of root activity, expressed as per unit root dry weight, which might be responsible for decreased N concentration in roots.

Estimation of soil reinforcement by the roots of four postdam prevailing grass species in the riparian zone of Three Gorges Reservoir, China

Soil erosion and bank degradation is a major post-dam concern regarding the riparian zone of the Three Gorges Reservoir. The development and succession of vegetation is a main countermeasure,especially to enhance bank stability and mitigate soil erosion by the root system. In this study, the roots of four prevailing grass species, namely, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, in the riparian zone were investigated in relation to additional soil cohesion. Roots were sampled using a single root auger. Root length density（RLD） and root area ratio（RAR） were measured by using the Win RHIZO image analysis system. Root tensile strength（TR） was performed using a manualdynamometer, and the soil reinforcement caused by the roots was estimated using the simple Wu＇s perpendicular model. Results showed that RLD values of the studied species ranged from 0.24 cm/cm3 to20.89 cm/cm3 at different soil layers, and RLD were significantly greater at 0–10 cm depth in comparison to the deeper soil layers（＆gt;10 cm）. RAR measurements revealed that on average 0.21% of the reference soil area was occupied by grass roots for all the investigated species. The measured root tensile strength was the highest for P. paspaloides（62.26MPa） followed by C. dactylon（51.49 MPa）, H.compressa（50.66 MPa）, and H. altissima（48.81MPa）. Nevertheless, the estimated maximum root reinforcement in this investigation was 22.5 k Pa for H.altissima followed by H. compressa（21.1 k Pa）, P.paspaloides（19.5 k Pa）, and C. dactylon（15.4 k Pa） at0–5 cm depth soil layer. The root cohesion values estimated for all species were generally distributed at the 0–10 cm depth and decreased with the increment of soil depth. The higher root cohesion associated with H. altissima and H. compressa implies their suitability for revegetation purposes to strengthen the shallow soil in the riparian zone of the Three Gorges Reservoir. Although the soil reinforcement induced by roots is only assessed from indirect indicators, the present results still useful for species selection in the framework of implementing and future vegetation recovery actions in the riparian zone of the Three Gorges Reservoir and similar areas in the Yangtze River Basin.

Growth of Young Olive Trees: Water Requirements in Relation to Canopy and Root Development

The study was carried out in northTunisia(36.5?N, 10.2?E) in order to get a comprehensive view of the growth dynamic of young olive orchards (Olea europaea L.,). The experiment involved irrigated trees of cultivars Chétoui, Manzanille, Meski and Picholine, planted at 6 ×6 m2spacing. Tree height, shoot length and canopy, fruit and trunk diameters were monitored regularly after plantation on 12 trees per variety. Root development was analyzed on Chétoui trees, only. Growth patterns were established annually for each variety before proposing an average model for each growth parameter. Results showed that tree height, shoot length and trunk diameter grew following an S-shaped curve with maximum annual increases occurring on the 4th year for tree height and a year later for canopy. The minimum gain coincided with the highest fruit load year, indicating that competition for assimilates concerns also young trees. Average growth patterns for tree height and shoots showed sustained rates all over the growing season with seven distinct periods of growth. Rapid growth occurred in April, July, and September, with similar growth trends observed for productive and less productive cultivars. However, the studied varieties behaved differently. Picholine cv., provided the most important increases and was the best water user. Results also showed that most roots were confined to the top soil layers and developed nearby the trunks. High root densities and important water depletion were observed in this area and thus, water and fertilizers should be supplied for young trees at these depths and distances from trunks. Root and canopy development were highly correlated (r = 0.94) and interfered with fruit growth. When trees set their first productions, the root-canopy ratio approximated the unit. An optimum ratio between root length and leaf area was found (2.3 km·m?2) for the 6-year-old tree, indicating good equilibrium between the above and the underground parts. On the basis of these results, a mathematical model was developed allowing a precise estimation of water requirements of olive trees during a period, where ground cover rarely exceeds 30%. We can conclude that all these models, graphic and mathematic give precise information on the occurrence of the various phenophases of young olive trees and may be used for a quantitative appraisal of the performance of olive varieties under a given environment. However, some aspects would be probed deeper and particularly the influence of climatic data on growth dynamic.

Differential responses of root growth to nutrition with different ammonium/nitrate ratios involve auxin distribution in two tobacco cultivars

Nitrogen(N), the major forms of which are nitrate(NO3–) and ammonium(NH4+), plays an important role in plant growth and mediation of root development. However, the role of auxin in root growth in response to different NH4+/NO3– ratios remains unclear. Two tobacco cultivars(Nicotiana tabacum L.) were adopted in this study, which displayed variant growth features under the situations with sole NO3– nutrition ratio(NH4+/NO3– ratio: 0/100), low NO3– nutrition ratio(NH4+/NO3– ratio: 97/3), and optimal NH4+/NO3– ratio(50/50). We investigated the effects of the different NH4+/NO3– ratios on the formation and elongation of lateral roots(LRs), auxin concentration, DR5::GUS expression, 3 H-labeled indole acetic acid([3 H]IAA) transport, and the expression of six PIN genes in tobacco roots. We also examined the effects of exogenous auxin and a transport inhibitor on LRs growth. The results are shown as follows, compared to optimal N nutrition conditions, the biomass and nitrogen(N) accumulation were largely reduced by sole and low NO3– nutrition treatment in NC89, but no difference was observed in Zhongyan 100. In most cases, sole and low NO3– nutrition impaired the elongation and formation of firstorder lateral roots(1° LRs), only in NC89, thus reducing the root growth. IAA concentration and DR5::GUS expression levels decreased in roots when NC89 was subjected to sole and low NO3– nutrition media, suggesting that different NH4+/NO3– ratios affect the transport of auxin from leaves to roots. Results were similar following exogenous NAA application to low NO3– nutrition treated seedlings. Based on direct [3 H]IAA transport measurement, the transport of polar auxin from shoots to roots decreased due to low NO3– nutrition. PIN4 expression levels were markedly decreased in roots of NC89by sole and low NO3– nutrition, while they were unaffected in Zhongyan 100 roots. Overall, our findings suggest that LRs formation in tobacco seedlings is regulated by NH4+/NO3– ratios via modifying polar transport of auxin.

Surface Treatments Effect on Rainfall Canopy Interception and Runoff-Rainfall Ratio for in-Field Rainwater Harvesting

The purpose of this study was to ascertain the effectiveness of surface treatments to quantify the partitioning of rainwater falling on the runoff strips and basins as well as to determine the fraction of rainwater available to intercept by maize canopy and infiltrate into the root zone. The rainfall canopy interception （RCI） was estimated as a function of basin leaf area ratio per rain event. The runoffrainfall （RR） ratio was determined for both a single rainfall event and the whole growing season. Infiltration ratio of basin to runoff area was analysed for every unit millimeter of water that infiltrate in the runoff section, some additional of water will infiltrate in the basin area. The plateau value of RCI-rainfall relationships rendered about double in the wider （1.0-1.1 mm） compared to the narrow runoff strips （0.5-0.6 mm）. Statistically, the combined surface treatments （RSL x ML） affected the RR ratio with higher efficiency in bare 1 m runoff （27%） and the lower efficiency group （〈 10%） is associated with the widest runoff length covered with mulch. Variations in fractions of rainwater that can infiltrate into basins and runoffareas can lead one to select alternative strategies for water harvesting techniques.

Root to crown ratio of permanent teeth of people living in Shanghai

The aim of this study is to assess if there is a significant difference between crown to root ratio of male and female permanent teeth in Chinese people in Shanghai.Methods: For this purpose one thousand four hundred (700,male and 700,female) extracted teeth were collected between age 25-35 and the crown length (CL) and root length (RL) of permanent teeth were measured by a precise caliper.Statistical analyses were performed with the SPSS 17 software by Student's t-test method.Results: The mean crown length of permanent teeth of male was found to be larger than that of female except for maxillary central incisor and the mean root length of male was found to be comparatively larger than that of female.Conclusion: There was a significant difference in root to crown ratio (RL/CL) between male maxillary teeth and mandibular teeth and female ones.The RL/CL ratio of male tends to be larger than those of female in Shanghai population.

iRoot SP冷侧压法与热牙胶垂直加压法在C形根管充填治疗牙体牙髓病患者中的应用效果比较

目的:比较iRoot SP冷侧压法与热牙胶垂直加压法在C形根管充填治疗牙体牙髓病患者中的应用效果。方法:选取2021年1月至2021年12月该院收治的60例牙体牙髓病患者进行前瞻性研究,按照随机数字表法将其分为对照组和观察组各30例。两组均进行C形根管充填治疗,对照组采用热牙胶垂直加压法,观察组采用iRoot SP冷侧压法,比较两组充填效果(适填率、充填面积比),随访6个月时临床疗效,治疗前和治疗后1、2、3 d疼痛程度[数字评价量表(NRS)]评分,不良反应发生率,以及随访6个月时复发率。结果:两组适填率、充填面积比、治疗总有效率比较,差异均无统计学意义(P>0.05);治疗后1、2、3 d,观察组NRS评分均低于对照组,差异有统计学意义(P<0.05);观察组不良反应发生率为10.00%(3/30),低于对照组的33.33%(10/30),差异有统计学意义(P<0.05);观察组复发率为3.45%(1/29),低于对照组的28.57%(8/28),差异有统计学意义(P<0.05)。结论:iRoot SP冷侧压法行C形根管充填治疗牙体牙髓病患者,可减轻疼痛程度,减少不良反应,降低复发率,但充填效果和临床疗效与热牙胶垂直加压法相当。

社区人群心内膜下心肌活力率的影响因素研究

背景心血管疾病目前在全球范围仍然有很高的发病率和死亡率。心内膜下心肌活力率(SEVR)是侵入性血流动力学研究中分析左心室和主动脉压力曲线引出的一个指标,是评估心肌灌注的一个有价值的工具,在不同人群的心血管不良事件和死亡率方面也具有潜在的预测价值。无创的测量方法可以估测SEVR,虽然有一定局限性,但仍然是评估心肌灌注和心血管风险的有价值的工具并显示出了巨大的临床应用潜力。目前缺乏大规模流行病学调查研究探索SEVR在心血管疾病一级和二级预防中的实际价值。目的在北京社区人群中使用无创方法估测SEVR,并分析其相关影响因素。方法本文基于队列研究的横断面随访,研究对象来源于北京大学第一医院心血管内科2011年12月—2012年4月在北京市石景山区首钢社区建立的动脉粥样硬化研究队列,招募人群为年龄≥40岁的社区居民。2018年随访时采用无创方法进行脉搏波分析检查,并获得SEVR结果。采用线性回归分析探究SEVR的相关影响因素。结果2018年参加随访的6568例研究对象中,排除因心律不齐等未能完成脉搏波分析检查获得SEVR者,最终入选6382例,97.2%的研究对象有SEVR结果。6382例社区居民中男2130例、女4252例,平均SEVR为(144±22)%。线性回归分析结果显示,在总社区居民中,性别(β=-11.00)、年龄(β=-0.53)、吸烟(β=2.36)、高血压(β=-4.12)、脂代谢紊乱(β=-1.45)、糖尿病(β=-4.36)、服用降压药(β=3.72)、降糖治疗(β=-3.71)是SEVR的独立影响因素(P<0.05)。在男性居民中,年龄(β=-0.67)、高血压(β=-3.20)、脂代谢紊乱(β=-2.73)、糖尿病(β=-3.42)及降糖治疗(β=-5.07)是SEVR的独立影响因素(P<0.05)。在女性居民中,年龄(β=-0.48)、吸烟(β=9.44)、高血压(β=-4.98)、糖尿病(β=-4.95)、服用降压药(β=5.26)及降糖治疗(β=-2.82)是SEVR的独立影响因素(P<0.05)。结论无创的SEVR测定在大规模社区人群的队列研究中应用是可行的。SEVR与性别、年龄、吸烟、高血压、脂代谢紊乱、糖尿病这些传统冠心病危险因素相关,其与药物治疗的关系还需要进一步研究探讨。

不同时期水分胁迫对大豆根系特性及产量的影响

为揭示抗旱基因型大豆根系应答干旱胁迫的响应机制,于2020年在辽宁省沈阳市开展盆栽试验,以抗旱基因型和干旱敏感型大豆为试材,探讨干旱(W1,土壤含水量为田间持水量的50%)、轻度干旱(W2,土壤含水量为田间持水量的60%)、适宜水分(W3,土壤含水量为田间持水量的80%)对大豆根系特性和产量的影响。结果表明:同一时期控水,W1和W2条件下,抗旱品种“辽豆14”的总根长和根表面积优于干旱敏感型品种“辽豆21”。一般情况下,平均根直径为0~0.5 mm的根长比例表现为:“辽豆21”>“辽豆14”,而平均根直径为0.5~1.0 mm的根长比例却表现为:“辽豆14”>“辽豆21”。随着生育进程的推进,大豆地上部鲜重、地上部干重、根干重逐渐累积,鼓粒期达最大值;一般情况下,同一控水时期,随着土壤含水量的增加,同一品种地上部鲜重、根鲜重、地上部干重、根干重值逐渐增加,但抗旱品种“辽豆14”的值一般优于干旱敏感型品种“辽豆21”。随着生育进程的推进,根冠比鲜重和根冠比干重值降低;土壤干旱提高了植株的根冠比。各个时期控水,品种和水分均显著影响了大豆的单株产量,干旱(W1)和轻度干旱(W2)均降低了2品种的单株产量,但抗旱品种“辽豆14”引起产量下降的值更低。干旱胁迫条件下,抗旱基因型大豆在总根长、根表面积、地上部干重、根干重、产量以及平均根直径为0.5~1.0 mm的根长比例方面,表现出优于干旱敏感型品种的优势。

影响‘红满堂’绿枝插条生根因子的研究

[目的]研究扦插基质、插穗部位、生长调节剂及生长调节剂处理时间对‘红满堂’品种绿枝扦插生根效果的影响,筛选绿枝扦插的适宜组合,可为其工厂化育苗提供理论依据和技术支撑。[方法]以‘红满堂’品种当年生绿枝为材料,采用L9(34)正交试验设计,从扦插后3 d开始,每3~4 d观察插穗基部变化,并记录插穗生根状况,在扦插50 d时,调查不同处理水平下插穗的生根率以及不定根数量、不定根均长和最长根长,综合评价生根效果。[结果]影响‘红满堂’品种绿枝扦插生根的主导因子是插穗部位,同一枝条发育充实、木质化程度相对较高的中、下部位插穗的生根率(36.67%、40.67%)显著高于上部插穗(9.33%)。生长调节剂的种类、浓度和处理时间长短是影响扦插繁殖的关键因素,对扦插繁殖的生根率、不定根条数、不定根均长、最长不定根长和生根效果综合评价值均有极显著影响,不同生长调节剂和时间处理‘红满堂’绿枝扦插的生根率、不定根条数、不定根均长、最长不定根长、生根效果综合评价值分别为14.67%~38.00%和23.33%~36.00%、2.40~5.03条和3.40~4.57条、1.93~2.27 cm和1.10~2.93 cm、2.47~3.41 cm和1.66~3.39 cm、43.70%~86.40%和56.00%~81.07%。扦插基质显著影响不定根的生长发育,不同基质的不定根条数、不定根均长、生根效果综合评价值分别为3.37~5.00条、1.34~3.10 cm、58.43%~76.37%。[结论]‘红满堂’品种绿枝扦插属综合生根类型,以愈伤组织生根类型为主。绿枝插穗生根最佳处理组合为:采用当年生绿枝下部做插穗,用生长调节剂IBA(吲哚丁酸)2500 mg·L^(-1)浸蘸插穗基部20 s,扦插于椰糠∶蛭石∶珍珠岩(1∶2∶4)的基质中。根系发育最佳的处理组合为:采用当年生绿枝的中间部位做插穗,用生长调节剂IBA 2500 mg·L^(-1)浸蘸插穗基部5 s,扦插于草炭∶蛭石∶珍珠岩(1∶2∶4)的基质中。

单粒精播对花生干物质累积及根冠结构的影响

为明确花生单粒精播增产机理,大田条件下,以花育22为供试花生品种,以双粒穴播(DS)为对照,研究了单粒精播(SS)对花生干物质积累、叶面积系数、冠层结构和根系特征的影响。结果表明,花生生育前期单株和群体干物质重单粒精播和双粒穴播差异不显著,而生育中后期显著高于双粒穴播,结荚期叶面积系数单粒精播显著高于双粒穴播。从结荚期不同冠层结构来看,冠层上、中、下层叶面积系数单粒精播分别比双粒穴播高23.03%、9.34%、86.43%,单株和群体冠层叶片和茎干重单粒精播均显著高于双粒穴播,从冠层不同部位叶片和茎干重占总干重的比例来看,单粒精播冠层下部叶片和茎干重比例高;单株和群体总根干重、根长、根表面积和根体积高于双粒穴播,且中下层根系占比高。相关性分析结果表明,根干重与中下层的叶片干重、下层的茎干重呈显著正相关。综上所述,与双粒播相比,单粒精播花生植株冠层中下部发育健壮且根系大分布深是其增产的重要原因。单粒精播促根扩冠,是花生节本增产的一种有效途径。

不同功能型沉水植物对溶解氧影响及环境效应

研究选用刺苦草(Vallisneria spinulosa)、黑藻(Hydrilla verticillata)和穗花狐尾藻(Myriophyllum spicatum)分别代表底层型、冠层少根型和冠层多根型沉水植物,通过中宇宙实验,探索不同功能型沉水植物在生长过程中水柱和沉积物中溶解氧(DO)浓度及其相关指标的差异。实验结果表明:不同处理组水柱DO浓度存在显著差异,空白组水柱DO浓度显著低于植物处理组,且空白组水柱总氮(TN)和总磷(TP)浓度降低程度最少;黑藻组比叶面积、叶面积指数、净增长生物量、相对生长速率和水柱DO浓度最大,能够有效降低水柱TP和TN浓度;穗花狐尾藻组株高最高,提升水柱DO浓度显著高于刺苦草,水柱TP降低程度最大;刺苦草组比根长、单株总根长和根冠比最大,提升沉积物深度6 cm以内的DO效果最好,沉积物铁含量最高,沉积物总氮(TN)、总碳(TC)含量和间隙水总溶解性磷(TDP)浓度最低。在修复富营养湖泊过程中,可根据水和沉积物缺氧状况,合理配置底层型和冠层型沉水植物,构建释氧能力较强的群落,从沉积物表层到水柱上层均为湖泊提供充足的氧气,从而更加有利于清水态的形成。

植被调控水土流失机制研究进展及展望

植被是调控水土流失的关键因子。从植被与水土流失关系的研究方法、植被调控土壤侵蚀的表征指标、植被不同部分(冠层、根系、枯落物)对土壤侵蚀的作用机制、植被对侵蚀泥沙分选性的影响机制、植被与其他因子交互作用的土壤侵蚀效应等5方面对植被调控水土流失机制的研究成果进行综述,并提出该领域的研究展望。笔者认为:植被盖度未达稳定值时其减沙的正向效应受到挑战,且植被盖度稳定值因土壤质地、植被类型和坡度而异,其机理尚不明确;在气候变化背景下,需要加强极端暴雨条件下植被根系促进浅层滑坡的机理研究;植被枯落物混入土壤后对土壤可蚀性的影响机理及其季节性变化机制有待进一步明晰;需加强植被覆盖下坡面径流水动力学特征及其对侵蚀泥沙颗粒分选性的影响机制研究,以及基于泥沙分选理论的林下土壤流失量化研究;植被与坡度、坡长、降雨强度等其他侵蚀因子交互作用的土壤侵蚀效应机理有待深入研究;另外,亟需研发包括植被参数、土壤参数、降雨和坡面流水动力学参数在内的植被侵蚀动力学方程,以推动土壤侵蚀物理模型的深入发展。

孕晚期血清尿酸及血清尿酸/肌酐水平与不良妊娠结局的关系研究

背景孕期血清尿酸代谢紊乱与不良妊娠结局相关,但目前分析并比较血清尿酸及血清尿酸/肌酐水平在孕期不良妊娠结局中的关系研究较少。目的分析孕妇孕晚期血清尿酸及血清尿酸/肌酐水平与不良妊娠结局的关系。方法选取2015—2022年于南京大学医学院附属鼓楼医院常规产检及生产的单胎活产孕妇743例为研究对象。根据是否发生不良妊娠结局,将孕妇分为正常组344例和不良结局组399例。分别以四分位数将血清尿酸及血清尿酸/肌酐分为3个水平:Q1(血清尿酸<257μmol/L)、Q2(血清尿酸257~359μmol/L)、Q3(血清尿酸>359μmol/L)和q1(血清尿酸/肌酐<5.88)、q2(血清尿酸/肌酐5.88~7.94)、q3(血清尿酸/肌酐>7.94)。根据孕妇中位年龄,将孕妇分为年龄<30岁亚组(341例)及年龄≥30岁亚组(402例)。根据既往孕产次情况,将孕妇分为初产妇亚组(539例)及经产妇亚组(194例)。采用多因素Logistic回归分析探讨血清尿酸及血清尿酸/肌酐水平与不良妊娠结局的关系。结果不良结局组孕妇年龄、BMI、血清尿酸、血清尿酸/肌酐、三酰甘油高于正常组(P<0.05)。校正混杂因素后,血清尿酸、血清尿酸/肌酐对不良妊娠结局影响的多因素Logistic回归分析结果显示,与Q1水平血清尿酸相比,Q3水平时子痫前期(AOR=4.41,95%CI=2.16~8.99)、宫内生长受限(AOR=3.59,95%CI=1.08~11.96)的发生风险增加(P<0.05);与q1水平血清尿酸/肌酐相比,q2、q3水平时子痫前期(AOR=2.33,95%CI=1.13~4.79;AOR=3.56,95%CI=1.68~7.56)的发生风险增加,q3水平时早产(AOR=2.76,95%CI=1.33~5.71)、宫内生长受限(AOR=5.15,95%CI=1.39~19.14)的发生风险增加,而q3水平时巨大儿(AOR=0.43,95%CI=0.19~0.98)、大于胎龄儿(AOR=0.38,95%CI=0.15~0.96)的发生风险降低(P<0.05)。血清尿酸、血清尿酸/肌酐在不同年龄亚组对子痫前期、早产的影响结果显示,与Q1水平血清尿酸相比,Q3水平在两个年龄亚组中子痫前期的发生风险均增加(P<0.05);与q1水平血清尿酸/肌酐相比,q2、q3水平在年龄≥30岁孕妇中子痫前期的发生风险增加(P<0.05)。血清尿酸、血清尿酸/肌酐在不同孕产次亚组对子痫前期、早产的影响结果显示,与Q1水平血清尿酸相比,Q3水平在初产妇中子痫前期的发生风险增加(P<0.05);与q1水平血清尿酸/肌酐相比,q2、q3水平在初产妇中子痫前期的发生风险增加,q3水平在初产妇中早产的发生风险增加(P<0.05)。结论高水平血清尿酸、血清尿酸/肌酐时子痫前期、宫内生长受限的发生风险均增加,其中子痫前期主要发生在年龄≥30岁的孕妇或初产妇中。高水平血清尿酸/肌酐时早产的发生风险增加,主要发生在初产妇中。血清尿酸/肌酐较血清尿酸预测的不良妊娠结局更多。